Navigational trapezoid

ABSTRACT

A navigational trapezoid to trace courses and azimuths on a chart and to inversely measure courses and azimuths in the form of an isosceles trapezoid to which an auxiliary ruler is coupled, the trapezoid having two opposite sides inclined at an angle of 45* to the larger base, and the trapezoid having two engraved protractors, one for use with longitudes of a chart as reference and the other for use with the latitudes as reference, the trapezoid also being engraved with lines parallel to the bases, and the auxiliary ruler also having lines engraved parallel to those of the trapezoid besides having a linear scale.

O United States Patent 1151 r 3,673,690 De Barros 1 1 'July 4, 1972 [54] NAVIGATION/KL TRAPEZOID FOREIGN PATENTS 0R APPLICATIONS Inventor: Fernando De Barres. Rua d9 nto io 1,028,256 2/1953 France ..33/108 candldo-lme ss= 627,582 3/1936 Germany ..33/108 [22] Filed: March 16, 1970 Primary ExaminerRobert B. Hull [21] 19690 Anorney-Browdy and Neimark [52] U.S. Cl ..33/75, 33/108 57 STR T [51] Int. Cl ..B43l13/02 58 Field of Search ..33/108, 1 SB, 104, 75 R A navlsallonal p to courses and aZ'mulh-S a chart and to inversely measure courses and azimuths in the 56] R fg g Cit d form of an isosceles trapezoid to which an auxiliary ruler is coupled, the trapezoid having two opposite sides inclined at an UNITED STATES PATENTS angle of 45 to the larger base, and the trapezoid having two 618,135 1/1899 Saunders et al ..33/75 R engraved pr9trac19rs.9ne for use with longiwdes a char! as 183,076 10/1876 Somes .,33/ 104 reference and the other for use with the latitudes as reference, 1,470,530 l0/l923 Hohmann. .....33/104 the trapezoid also being engraved with lines parallel to the 1,746,537 2/1930 Knechtelubases, and the auxiliary ruler also having lines engraved paral- 2,332,100 v Maciean ---3 R lel to those of the trapezoid besides having a linear scale. 3,271,866 9/1966 Gruber et al. ....33/75 R 3,289,299 12/ l 966 Elger ..33/104 4 Claims, 1 Drawing Figure NAVIGATIONAL TRAPEZOID This present invention relates to a navigational aid and, more particularly, to a navigational set-square.

A simple, multi-use navigational assisting device of low cost has long been a need of navigators. The present invention has for an object the provision of such a navigational aid in the form of an isosceles trapezoid to which an auxiliary ruler is coupled with the sides of the trapezoid being inclined to the larger base of the trapezoid at a 45 inclination.

It is, accordingly, an object of the present invention to assist a navigator in ease of accurately navigating a course.

It is another object of the present invention to provide an improved navigational device which incorporates a coupled isosceles trapezoid and an auxiliary ruler.

It is another object of the present invention to overcome the defects in the prior art, such as indicated above.

To the attainment of these ends and the accomplishment of the above as well as other new and useful objects of the invention as will appear below, there will now be described a possible embodiment thereof for a better understanding of the invention, it being understood that this embodiment is to be intended as merely exemplary and in no way limitative, with reference to the attached drawing, in which:

The FIGURE is a plan view of an embodiment of the device in accordance with the present invention.

In general, the navigational trapezoid or set-square shown in the accompanying drawing comprises two elements, namely an isosceles trapezoid l and an auxiliary ruler l2, hingedly connected together and formed of a rigid transparent material, such as methyl methacrylate polymer (Lucite or Plexiglas"). It will be seen that the isosceles trapezoid has a larger base 14, a smaller base 16, and two inclined and opposite sides 18 and 20. The sides 18 and are inclined from the base 14 by an angle of 45 and, accordingly, if these sides 18 and 20 are extended beyond the small base 16, they meet at aright angle.

The trapezoid has, either engraved or otherwise provided on its upper surface, two protractors, in the illustrated embodiment one being provided along the two sides and the small base 16 and the other being provided in a semi-circle internally along the body of the isosceles trapezoid. In practice, one such protractor, preferably the external one, is provided in a color such as black, whereas the internal protractor is provided in another color, such as red. The black external protractor is intended to be used with the longitudes of a navigational chart as reference while the red internal protractor is intended to be used with the latitudes of such chart as reference. In addition, the trapezoid 10 is provided with a series of lines parallel to the bases 14 and 16, the purposes of which are described in detail below. Similarly, the auxiliary ruler 12 also has lines parallel to those of the trapezoid for the same purpose, and in addition has a linear scale on its outside edge, in the illustrated embodiment the scale being in centimeters and millimeters.

It will be noted from the figure that the isosceles trapezoid l0 and the ruler 12, located in the same plane, are rotatably hinged together by means of a pair of parallel links 22 and 24, each being pivotally connected to the ruler 12 at pivots 220 and 240, respectively, and to the isosceles trapezoid 10 at the pivots 222 and 242, respectively. It will be clear that the distance between the pivots 222 and 242 is equal to the distance between the two pivots 220 and 240.

The primary usage of the navigational trapezoid is to trace courses and azimuths on a chart; and to inversely measure courses and azimuths. One trapezoid by itself is sufficient to rapidly and accurately solve the problems indicated. Cases may occur, however, in which, due to the lack of latitudes and longitudes such as in old charts, or due to a large distance between points, the navigational trapezoid becomes more useful if it is used along with any ruler or set-square to extend its length or to slide it along either of its sides so moving the trapezoid parallel to its bases.

The navigational trapezoid has, however, other applications including the determination of correct course and position by successive bearings from a given object; the approximate determination of the position of a ship by means of successive soundings; the provision of a compass with three points (station pointer) to determine the position of a ship or to determine the compass deviation from three bearings, provided that the sum of the observed angles is less than 180; and the tracing of parallel and perpendicular lines by sliding one of the sides of the trapezoid over an auxiliary straight edge, since the sides form a right angle.

The various uses of the navigational trapezoid in accordance with the present invention will be defined in more detail below by reference to the following examples, it being understood that these examples are illustrative and not limitative:

EXAMPLE 1 Tracing Courses and Azimuths Through a Definite Point 1.

a. Select the longitude (or latitude) most convenient to be used as a reference line;

b. Position the navigational trapezoid approximately on the wanted course or azimuth, placing the external base of the auxiliary parallel ruler near the point under consideration;

0. Position the trapezoid so that the center of the protractors coincide with the reference longitude (or latitude) and so that the wanted course or azimuth can be read on the external (or internal) protractor;

d. Keep the trapezoid in the same position and move the auxiliary ruler until its external edge coincides with the point under consideration (or make the internal edge of the auxiliary ruler, or one of the bases of the trapezoid coincide with the point under consideration);

e. Use this edge to trace the course or azimuth required.

2. Courses and azimuths can also be traced starting from a compass rose printed on the chart. In this case the navigational trapezoid is used like any parallel ruler. 3. The position of the trapezoid can be inverted if convenient. 4. Except in the limiting case, there are always two positions of the auxiliary ruler from which the same course or azimuth can be traced. This has the effect of increasing the useful length of the ruler.

EXAMPLE 2 Measuring Courses and Azimuths l.

a. Place one of the external (or internal) edges, or any edge with an engraved scale as convenient, along the line of the course or azimuth to be measured;

b. Secure the auxiliary ruler and move the trapezoid until the center of the protractors coincides with the longitude (or latitude);

c. Read the course or azimuth from the external (or internal) protractor.

2. The reading can also be taken from the compass rose printed on the chart.

3. The position of the trapezoid can be inverted if convenient. 4. When reading angles, it is always necessary to bear in mind that:

a. In the first quadrant the courses and azimuths are between 0 and b. In the second, between 90 and c. In the third, between 180 and 270";

d. In the fourth, between 270 and 360.

EXAMPLE 3 Determining the Correct Course and Position from Bearings 1. Trace on the chart the successive bearings of the object. 2. Mark on the base the distances covered during the observa- V tions using the same scale as the chart.

EXAMPLE 4 EXAMPLE 5 Use as a Station Pointer Determining the angles on the left and the right hand side on the lower face and adjust the trapezoid as if it were a station pointer.

The required position is the center of the protractors which can be obtained by a simple construction marking on the chart the point of theiperpendicular bisector of the bases of the trapezoid and the external edge of the auxiliary ruler and mark along the same perpendicular bisector a distance equal to the distance between the origin of the protractors and the same external edge.

EXAMPLE 6 Determining the Needle Deviation from the Bearing of Objects I 1. Trace on the chart the respective bearings thus obtaining the position triangle. 2. Use the ruler as if it were a station pointer, tracing the sides of the angles on the left hand side found from the three bearings on the-lower face.

Determine the correct position.

3. The deviation is the angle between the bearing taken on the objects and that taken from the chart starting from the correct point.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specifica- 4 tion.

What is claimed is:

1. An improvement of parallel ruler and made of transparent material hingedly connected along its larger base to an auxiliary ruler, the sides of said isosceles trapezoid having an inclination of 45 to the larger base, wherein said isosceles trapezoid has two engraved protractors, one, marked around the periphery of said trapezoid, meant to be used with the iongitudes of the chart as references, and the other, marked within the periphery of said trapezoid and whose scale numberings are made of transparent material, an auxiliary ruler and parallel links hingedly connecting said trapezoid along its larger base to said auxiliary ruler, the sides of said isoceles trapezoid having an inclination of 45 to the larger base, wherein said isoceles trapezoid has two engraved protractors, one, marked around the periphery of said trapezoid in degrees numbered for use with the longitudes of the chart as references, and the other, marked within the periphery of said trapezoid in numbered degrees and whose numberingsare rotated with respect to the first named protractor, for use with latitudes as references.

2. An improvement of parallel ruler and navigation setsquare in accordance with claim 1 wherein said isoceles trapezoid has engraved lines parallel to the bases-for coincidence with the line of the course or azimuth and reading from the compass rose printed on the chart.

3. An improvement of parallel ruler and navigation setsquare in accordance with claim 2 wherein said auxiliary ruler has engraved lines, parallel to the engraved lines of the trapezoid and for the same purpose.

4. An improvement of parallel ruler and navigation setsquare in accordance with claim --l wherein one of said protractors is marked in one color and the other of said protractors is marked in a second contrasting color.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,673,690 Dated July It, 1972 InVent0r(5) Fernando De Barros It is certified that error appears in the above-identified patent and that said Letters. Patent are hereby corrected as shown below:

Amend claim 1, (column it) to read as follows:

"1. An improvement of parallel ruler and navigation set square, comprising an isosceles trapezoid made of transparent material, an auxiliary ruler and parallel links hingedly connecting said trapezoid along its larger base to said auxiliary ruler, the sidgs of said isosceles trapezoid having an inclination of A5 to the larger base, wherein said isosceles trapezoid has two engraved protractors, one, marked around the periphery of said trapezoid in degrees numbered for use with the longitudes of the chart as references, and the other, marked within the periphery of said trapezoid in numbered degrees and whose numberings are rotated 90 with respect to the first named protractor for use with latitudes as references."

Signed and sealed this 23rd day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer 7 Commissioner of Patents F ORM PO-1050 (10-69) USCOMM-DC 60376-P69 u.s, GOVERNMENT PRINTING OFFICE: I969 o-ase-asa 

1. An improvement of parallel ruler and made of transparent material hingedly connected along its larger base to an auxiliary ruler, the sides of said isosceles trapezoid having an inclination of 45* to the larger base, wherein said isosceles trapezoid has two engraved protractors, one, marked around the periphery of said trapezoid, meant to be used with the longitudes of the chart as references, and the other, marked within the periphery of said trapezoid and whose scale numberings are made of transparent material, an auxiliary ruler and parallel links hingedly connecting said trapezoid along its larger base to said auxiliary ruler, the sides of said isoceles trapezoid having an inclination of 45* to the larger base, wherein said isoceles trapezoid has two engraved protractors, one, marked around the periphery of said trapezoid in degrees numbered for use with the longitudes of the chart as references, and the other, marked within the periphery of said trapezoid in numbered degrees and whose numberings are rotated 90* witH respect to the first named protractor, for use with latitudes as references.
 2. An improvement of parallel ruler and navigation set-square in accordance with claim 1 wherein said isoceles trapezoid has engraved lines parallel to the bases for coincidence with the line of the course or azimuth and reading from the compass rose printed on the chart.
 3. An improvement of parallel ruler and navigation set-square in accordance with claim 2 wherein said auxiliary ruler has engraved lines, parallel to the engraved lines of the trapezoid and for the same purpose.
 4. An improvement of parallel ruler and navigation set-square in accordance with claim 1 wherein one of said protractors is marked in one color and the other of said protractors is marked in a second contrasting color. 